A new squid has been caught near Hawaii — much is being made of the fact that it has eight arms instead of ten, but that doesn’t seem like such a big deal to me, since we have the example of Taningia danae with a similar arrangement. It’s more interesting that there is a preliminary assignment to the genus Mastigoteuthis, a curious and poorly understood group of cephalopods.
Since I asked for it, and since so many were promptly forthcoming with a copy, I’d better give you a quick summary. Kubodera et al. have formally published their observations of the eight-armed deep sea squid, Taningia danae, that were in the news last February. There isn’t much new information in the papers; it’s all based on a handful of video observations of hunting squid in their native habitat, so it’s more on the side of anecdote than anything else right now. It’s still just plain cool.
That photo is of their video gear. It’s a platform with lights and cameras that’s lowered on a cable to almost a thousand meters. What I thought was cute, though, was that object jutting off at about 45°—that’s a fiberglas fishing pole with a short length of monofilament line dangling the bait in front of the cameras. It’s so jaunty to strap a pole to your robot and send it off to go fishing.
Somebody out there must be able to give me a fix—I keep trying to get this paper, and either my library gives me ambiguous messages about access and a few errors, or the Royal Soc. site balks and tells me that there is system maintenance going on. I can’t even get to the videos. Come on, man, I’m going through withdrawal here. I need a little taste. Please.
Kubodera T, Koyama Y, Mori K (2007) Observations of wild hunting behaviour and bioluminescence of a large deep-sea, eight-armed squid, Taningia danae. Proc Biol Sci 274(1613): 1029-34.
There’s got to be a fellow academic out there who’s willing to help out a squid junkie in need. If you can send me the pdf, I’ll owe you bigtime.
Thanks to Reginald Selkirk, Bob O’H, and Don S., I now have my fix. I’m squirting it into my brain through the eyeballs right now. I may have to go lie down for a while to let the good feelings linger.
This is pretty nifty — putting out a request and getting multiple replies in less than a half hour.
How else can I respond to this wretched rant against our beloved cephalopods last night? He claims that “Narrowing the gap between cephalopods and humans can only lead to disaster” and that “Our seafood is training for something big”, and he’s right—and the only appropriate response is to welcome our new tentacled masters. Defiance and threats, like those of Mr Colbert, will only hasten your subjugation.
The initial change from camouflaged to conspicuous takes only milliseconds due to direct neural control of the skin. Full expression of the threat display (right) is two seconds. Video frame rate is 30 frames per second. Watch the video clip.
Everyone here is familiar with the incredible ability of cephalopods to change their appearance, right? If you aren’t, review your cuttlefish anatomy and watch this video. A few frames from the video are shown on the right.
This is an amazing ability, and the question is how do they do it? Roger Hanlon has been spending years tinkering with cephalopods, trying to puzzle it out and come up with an explanation. There are a couple of things a master of disguise needs.
A good visual system. To match the background, you need to be able to see the background at least as well as the predator trying to see you.
Fast connections to the effector organs. Cephalopods have motor nerves that go straight from their brains to the chromatophore organs with no synaptic delays along the way.
The hard part: cutaneous chromatophore organs that can change intensity and texture with a fair amount of spatial resolution. Cephalopods have tiny, discrete sacs of pigment scattered all over their body, each one ringed with muscles that can iris shut to conceal the pigment, or expand the sac to expose the pigment. There are also muscular papillae that work hydrostatically to change the texture of the skin from smooth to rough to spiny/spiky.
An algorithm. A set of rules that translate a visual field into an effective skin pattern that hides the animal.
One of the minor surprises of this work is that that last item, the algorithm for generating camouflage, may not be that complex. By studying many camouflaged organisms, they’ve categorized camouflage techniques into just three different strategies.
